AJP valve seats

[Jhonno]

Heads are currently being refreshed.. Is there anything wrong with the standard AJP valve seats? Could have them replaced whilst it is in bits..

[ukkid35]

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

[Jhonno]

ukkid35 said:

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

Nope that would be it..

I can see if I can ask the machine shop to measure the ones they take out..

120mm is the original length..

[gruffalo]

Jhonno said:

ukkid35 said:

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

Nope that would be it..

I can see if I can ask the machine shop to measure the ones they take out..

120mm is the original length..

I have always understood it to be the stem stretching.

[Jhonno]

gruffalo said:

Jhonno said:

ukkid35 said:

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

Nope that would be it..

I can see if I can ask the machine shop to measure the ones they take out..

120mm is the original length..

I have always understood it to be the stem stretching.

That was my understanding.. Just wanted to check I was right.

No one looked at changing/improving the valve material to stop them doing this?

[ukkid35]

This photo is definitive proof that Intake valves are not the same length as exhaust when you remove them

I'm assuming they are the same length when new

I haven't even bothered measuring them the difference is so extreme

[gruffalo]

Jhonno said:

gruffalo said:

Jhonno said:

ukkid35 said:

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

Nope that would be it..

I can see if I can ask the machine shop to measure the ones they take out..

120mm is the original length..

I have always understood it to be the stem stretching.

That was my understanding.. Just wanted to check I was right.

No one looked at changing/improving the valve material to stop them doing this?

I think if you buy replacement valves now the new ones are less stretchy.

I had my engine rebuilt 20,000 or more miles ago and the valve gaps have not changed over that time.

[Jhonno]

ukkid35 said:

This photo is definitive proof that Intake valves are not the same length as exhaust when you remove them

I'm assuming they are the same length when new

I haven't even bothered measuring them the difference is so extreme

Wow!

[Jhonno]

gruffalo said:

Jhonno said:

gruffalo said:

Jhonno said:

ukkid35 said:

Has anyone been able to determine whether it is primarily the intake valve seats that wear, or the valve stems that stretch?

Can't be anything else that closes the clearance can it?

Nope that would be it..

I can see if I can ask the machine shop to measure the ones they take out..

120mm is the original length..

I have always understood it to be the stem stretching.

That was my understanding.. Just wanted to check I was right.

No one looked at changing/improving the valve material to stop them doing this?

I think if you buy replacement valves now the new ones are less stretchy.

I had my engine rebuilt 20,000 or more miles ago and the valve gaps have not changed over that time.

That is good to know! I have a full set of new Powers valves going in..

[Chimp871]

ukkid35 said:

This photo is definitive proof that Intake valves are not the same length as exhaust when you remove them

I'm assuming they are the same length when new

I haven't even bothered measuring them the difference is so extreme

Incredible! How many miles had the engine done?

[Byker28i]

Is that an old engine, based on I was told my old engine had old chrome valves so they needed replacing

[ukkid35]

Here are the vaves from the other head from my '98 4.5

In all respects it is in much better condition than the first head from which I posted pics

[GT6k]

So why does one (just one) of my intake valves have a steadily increasing gap ?

[Jhonno]

GT6k said:

So why does one (just one) of my intake valves have a steadily increasing gap ?

Increasing?!

[TwinKam]

GT6k said:

So why does one (just one) of my intake valves have a steadily increasing gap ?

That would point to wear somewhere (as opposed to stretching) and normally one would suspect the cam and follower as the most likely suspects, but as those are clearly visible when you have been measuring your clearances, presumably they look OK. So the next thing would be to check the shim, as I understand that there have been cases of them breaking up...

[FarmyardPants]

Yes maybe the valve head is working its way into the bucket

[GT6k]

Yes, no sign of wear on the cam or follower but the gap is slowly opening at about the same rate that every other inlet is closing.

[ukkid35]

GT6k said:

Yes, no sign of wear on the cam or follower but the gap is slowly opening at about the same rate that every other inlet is closing.

And each time the gap has increased you've fitted a thicker shim?

If so then there has to be something happening to the cam or lifter, or possibly the cam caps (but that would affect exhaust as well)

Worn lifters look very obviously worn, so I am at a loss

[ukkid35]

ukkid35 said:

This photo is definitive proof that Intake valves are not the same length as exhaust when you remove them

I'm assuming they are the same length when new

Never assume anything!

They are NOT the same length when new

I have just bought a pair of valves to drop off at the engineer who is repairing the head damage, and the new intake is longer than the new exhaust

Therefore all my photos above have very little value

I didn't have any way of measuring anything with me, but I did have the old intake valves

When I compared the old vs new intakes using the crudest method possible, in the car, sitting them on the dash, it was still obvious that the old valve was longer than the new

So, I reckon they really do stretch with age



I'll be able to do a more accurate test once I've spent a small fortune on parts and cylinder head repairs

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[ukkid35]

New Intake valve from TVR Parts are precisely 120.00mm

New Exhaust valves from TVR Parts are precisely 190.00mm

My old Intake valves are 120.30mm

My old exhaust valves are 190.00mm

"Proof that intake valve stretch" is the issue

Except that almost 2mm of variation is handled by shim changes (1.47mm to 3.00mm)

My conclusion is that intake valve stretch is real, but not that significant

Edited by ukkid35 on Thursday 2nd August 05:51